Cellular system

ABSTRACT

A cellular system using a code division multiple access (CDMA) scheme includes N (N is a positive integer) pilot channels and M (M is a positive integer) data channels. The pilot channels are used transmitting reference signals whose transmission signals are known in advance. The data channels are used for transmitting information. Each of the M data channels is made to correspond to one or a plurality of said N pilot channels.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation of U.S. patent application Ser. No. 09/260,903,filed Mar. 2, 1999 now U.S. Pat. No. 7,072,325, in the name of ToshifumiSATO, and entitled CELLULAR SYSTEM.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a mobile telephone/portable telephonesystem (cellular system) using a direct spread code division multipleaccess (DS-CDMA) scheme and, more particularly, to a cellular systemcharacterized by a transmission method using pilot channels for coherentdetection and transmission power control.

2. Description of the Prior Art

As a conventional technique of the present invention, an IS-95 system asa standard cellular system in North America is available.

In a forward link (base station→mobile terminal) according to the IS-95specifications, a pilot channel commonly used for channels for allmobile terminals is prepared, and signals are constantly transmitted byusing about 20% of the base station transmission power. On the pilotchannel, a single spread code having a relatively large length (a 2¹⁵chip period=about 26.6 ms) is used, and a non-modulated signal (i.e.,normally “0”) is transmitted. The reception section of a given mobileterminal estimates the transmission path of the radio signal received byusing this pilot channel (estimates the delay, phase, and amplitude).This transmission path is used to determine the de-spreading timing of adata channel addressed to the given mobile terminal and perform coherentdetection and RAKE combining.

Another conventional technique is a wideband CDMA scheme (to be referredto as a W-CDMA hereinafter), which has not been put into practice. TheW-CDMA is a scheme. that has been studied for the third-generationcellular system (IMT-2000). Currently, in Japan, IMT-2000 standardsproposals are being prepared by the Association of Radio Industries andBusinesses (ARIB).

According to a conventional proposed W-CDMA scheme, a known pilot symbol(since this data is time-multiplexed with another data, it is called apilot symbol instead of a pilot channel unlike in IS-95) is added to achannel directed to each mobile terminal.

In IS-95, a pilot channel is prepared in only a forward link. In theconventional W-CDMA, pilot channels are prepared for the respective datachannels, and hence a pilot symbol is also added to a reverse link(mobile terminal → base station). The reception sections of a mobileterminal and a base station estimate a transmission path by using thispilot symbol as in IS-95, and the estimated transmission path is used todemodulate data through a data channel addressed to itself.

A pilot symbol is added to each data channel in W-CDMA in this manner touse an efficient coherent detection scheme by estimating a transmissionpath using the same method in both a reverse link and a forward link,thereby improving the reverse link quality. Another purpose of theaddition of such pilot symbols is to reduce radio wave radiation inunnecessary directions by changing the directivity of the base stationantenna for each mobile terminal in a forward link so as to improve theforward link quality.

This method is called an adaptive antenna (adaptive array antenna) orsmart antenna technique. This technique is a kind of space divisionmultiple access (SDMA) in terms of reuse of radio waves upon spacedivision. In a CDMA cellular system, in which radio waves having thesame frequency are used in all the cells, the SDMA is regarded as apromising future technique.

The first problem in the prior art is that the method of preparing acommon pilot channel to all terminals as in IS-95 described above doesnot match well with the technique of controlling transmissiondirectivity for each mobile terminal by using an adaptive antenna array.

That the antenna directivity of the base station changes for therespective mobile terminals means that a pilot channel through whichreference signals are uniformly transmitted in all terminal directionsdiffers in transmission paths from a data channel through whichinformation is transmitted by an antenna whose directivity is focused onthe self-terminal, and the transmission path estimation result obtainedby using the pilot channel cannot be used to demodulate the informationthrough the data channel. For example, some of multipath channelsdetected by using the pilot channel may fall outside the data channeldirectivity range. In addition, there is no guarantee that the carriersare in phase.

The second problem in the prior art is that in the method of adding apilot symbol to each channel as in the conventional W-CDMA scheme, theoverheads of the pilot symbols become excessively large, resulting inpoor transmission efficiency, especially in speech communication at alow data rate.

In the conventional W-CDMA scheme, four pilot symbols are transmitted at0.625-ms intervals, which can be regarded as an overhead correspondingto 4.26 kbps in consideration of error correction code efficiency=⅓.This overhead is not small as compared with a data rate forhigh-efficiency speech, e.g., 8 kbps.

The third problem in the prior art is that when a pilot symbol is addedto each data channel, since large power cannot be assigned, ahigh-quality reference signal cannot be obtained, although about 20% ofthe total transmission power of the base station can be assigned toobtain a high-quality reference signal when a common pilot channel isused as in IS-95 described above. The reference signal with poor qualitymust be improved by, for example, filtering. This influences thecomplexity of each terminal.

An adaptive array antenna is a future technique and hence should not beused in consideration of cost in the early stage of introduction. It ispreferable that investment in equipment be made without any adaptivearray antenna in the early stage of introduction, and investment in thistechnique as an improved technique is made with an increase in traffic.

Transmission path estimation does not depend on data rates. For thisreason, when a high data rate is set, e.g., when data services areoffered at 384 kbps, the overhead of a pilot symbol can be neglected.When, therefore, low-speed voice services are mainly offered, the commonpilot channel scheme is advantageous, and the individual pilot channelscheme will become an indispensable technique in the future regardlessof whether high-speed data services are mainly offered. Therefore, thereare demands for a flexible scheme capable of smoothly coping withchanges in services in this manner.

SUMMARY OF THE INVENTION

The present invention has been made in consideration of the abovesituation in the prior art, and has as its main object to provide acellular system incorporating a flexible reference signal transmissionmethod capable of selecting an optimal apparatus arrangement inaccordance with the contents of a required service.

It is another object of the present invention to provide a transmissionmethod which can obviate the necessity to change a pilot channel/datachannel assigning method even if a system is optimized from a systemintroduction period in which voice services are mainly offered with arelatively small traffic to a system expansion period in whichhigh-speed data services are offered with a large traffic.

It is still another object of the present invention to simplify a mobileterminal apparatus when voice services are to be mainly offered, improvethe transmission efficiency, and efficiently accommodate high-speed dataservices when an SDMA technology is established in the future.

In order to achieve the above objects, according to the basic aspect ofthe present invention, there is provided a cellular system comprisingtransmission sections having N pilot channels, transmission/receptionsections having M data channels, a plurality of antenna elements, aweighting matrix for antenna for generating L types of antennadirectivity patterns by weighting the phases and amplitudes of signalstransmitted from the respective transmission sections andtransmission/reception sections and supplying the resultant signals tothe respective antenna elements, a control section for supplyingweighting coefficients to the weighting matrix for antenna and notifyinga correspondence between data and pilot channels by using a controlchannel, and a transmission/reception section having a control channelfor notifying a pilot channel corresponding to a data channel used forcommunication to each mobile terminal.

The present invention is characterized in that a combination of pilotand data channels is not fixed but can be dynamically changed inaccordance with the use state of the data channel.

In this manner, a plurality of pilot channels are dynamically assignedin accordance with the use state of each data channel to allow aplurality of data channels having the same antenna directivity to sharea pilot channel, thus effectively using pilot channel resources.

Even if a conventional system with a fixed antenna directivity shifts toan advanced system designed to realize space division reuse offrequencies by controlling the antenna directivity of an adaptiveantenna array or the like, there is no need to change a pilotchannel/data channel assigning method. Such a shift can therefore beeasily made.

Another effect of the present invention is that the channel capacity canbe maximized in accordance with a system configuration.

This is because interference acting on other channels can be minimizedby transmitting signals using the necessary minimum number of pilotchannels.

The third effect of the present invention is that a very flexible systemcan be realized.

This is because even if a conventional system with a fixed antennadirectivity shifts in the future to an advanced system designed torealize space division reuse of frequencies by controlling the antennadirectivity of an adaptive antenna array or the like, there is no needto change a pilot channel/data channel assigning method, and the shiftcan therefore be easily made.

The above and many other objects, features and advantages of the presentinvention will become manifest to those skilled in the art upon makingreference to the following detailed description and accompanyingdrawings in which preferred embodiments incorporating the principle ofthe present invention are shown by way of illustrative examples.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing a base station apparatus according tothe basic aspect of the present invention;

FIG. 2 is a view for explaining the correspondence between antennadirectivities, pilot channels, and data channels in the basic aspect;

FIG. 3 is a flow chart showing the operation of the basic aspect;

FIG. 4 is a block diagram showing an example of the arrangement of apilot channel transmission section;

FIG. 5 is a block diagram showing an example of the arrangement of adata channel transmission/reception section; and

FIG. 6 is a block diagram showing an example of the arrangement of aweighting matrix for antenna and antenna elements.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The basic aspect of the present invention will be described first withreference to the accompanying drawings.

FIG. 1 is a block diagram showing a base station apparatus according tothe basic aspect of the present invention. This basic aspect isassociated with a cellular system for performing communication betweenthe base station apparatus and mobile terminals.

Referring to FIG. 1, the base station apparatus is comprised oftransmission sections 101 to 103 having N (N is a positive integer)pilot channels, transmission/reception sections 104 to 106 having M (Mis a positive integer) data channels, a plurality of antenna elements109, a weighting matrix for antenna 108 for generating L (L is apositive integer) types of antenna directivities patterns by weightingthe phases and amplitudes of signals transmitted from the transmissionsections 101 to 103, the transmission/reception sections 104 to 106, anda transmission/reception section 107 and supplying the resultant signalsto the respective antenna elements 109, a control section 110 forsupplying weighting coefficients to the weighting matrix for antenna 108and making the data channels correspond to the pilot channels, and thetransmission/reception section 107 having a control channel fornotifying each mobile terminal of a pilot channel corresponding to thedata channel to be used for communication on the basis of a command fromthe control section 110. The operation of the basic aspect in FIG. 1will be described next.

Referring to FIG. 1, reference symbols PL₁ to PL_(N) denote transmissionsignals on pilot channels 1 to N; Tch₁ to Tch_(M),transmission/reception signals on data channels (also called trafficchannels) 1 to M; and P₁ to P_(N), transmission control signals (forON/OFF control for transmission, instruction about transmission power,and the like) for pilot channels 1 to N.

On data channels 1 to M, the direction of a mobile terminal that isperforming communication is estimated on the basis of reception, and thecontrol section 110 is notified of the estimated mobile terminal. Thecontrol section 110 determines the optimal antenna directivity. If thedetermined antenna directivity is being used on another data channel,and the corresponding pilot channel is being used for transmission, thecontrol section 110 notifies the mobile terminal of the correspondingpilot channel number (or spread code) through the control channel. Ifthis antenna directivity is not being used, an available pilot channelis selected to start transmission with the designated antennadirectivity.

If the position of the mobile terminal is unknown before speechcommunication, communication may be started with an omni-directivityfirst, and the antenna directivity and corresponding pilot channel maybe changed when the direction of the mobile terminal is estimated.

If excess overhead results when pilot channels are separately set, as invoice terminals, wastes resulting from the overhead can be reduced byassigning a common pilot channel to a plurality of terminals.

When communication through a given data channel is complete, and anotherdata channel does not share the corresponding pilot channel,transmission is stopped by using the corresponding pilot channel. Ifanother data channel shares the pilot channel, transmission is continuedby using the pilot channel.

FIG. 2 is a view for explaining the correspondence between antennadirectivities and pilot and data channels in the basic aspect.

FIG. 2 shows an example of how pilot and data channels are assigned inaccordance with antenna directivity patterns and the positions of mobileterminals. At this time, the antenna elements 109 are using four typesof directivity patterns and pilot channels PC₁ to PC₄. Any directivitypattern in a direction in which no terminal is performing speechcommunication is not used.

The pilot channel PC₁ covers all directions. This channel is used by amobile terminal whose position is not detected immediately after thestart of speech communication, an in-car terminal that is moving near abase station BS at a high speed (i.e., a terminal whose directionchanges at short intervals when viewed from the base station), or thelike. The pilot channels PC₂ and PC₃ are shared among a plurality ofdata channels located in the same directions. The pilot channel PC₃ isshared among a plurality of voice terminals, and has a relatively widedirectivity pattern. A data channel DC₈ is a high-bit-rate channel, towhich one pilot channel PC₄ is exclusively assigned. This channelreduces interference with other channels by using a narrow antennadirectivity pattern.

FIG. 3 is a flow chart showing the operation of the basic aspect.

Referring to FIG. 3, when communication is to be started, an availabledata channel is found first to ensure a data channeltransmission/reception means (step F-1). If the direction of the mobileterminal is known at this time, the optimal antenna directivity for thedirection of the mobile terminal is selected. If the direction of themobile terminal is unknown, an antenna directivity in all directions inwhich the mobile terminal can exist may be selected (step F-2).

If another terminal exists in the direction of this antenna directivityand is performing communication (step F-3), since this terminal isperforming transmission with the antenna directivity by using-a pilotchannel, this pilot channel may be used. That is, any new pilot channeltransmission means need not be ensured. If this antenna directivity isunused (step F-3), an available pilot channel transmission means isensured, and transmission is started by using the pilot channel (stepF-4).

Subsequently, pilot and data channel numbers (or spread codes)indicating the channels to be used by the mobile terminal are notifiedby using the control channel to start transmission/reception by usingthe data channel (step F-6).

Assume that the optimal antenna directivity changes as in case whereinthe position of the mobile terminal has moved to the end of the antennadirectivity during communication, or the direction of the mobileterminal, which was unknown at the start of communication, is knownafter a period during which transmission/reception is performed with awide directivity (step F-7). In this case, processing in step F-3 andthe subsequent steps are performed for the new antenna directivity.Whether a change in antenna directivity is required is periodicallymonitored during communication.

When the communication is complete (step F-8), thetransmission/reception using the data channel is stopped to release thedata channel transmission/reception means (step F-9). If the same pilotchannel is not being used by another data channel (step F-10), thetransmission using the pilot channel is also stopped to release thepilot channel (step F-11). If the same pilot channel is being used byanother data channel (step F-10), the processing associated with thedata channel is terminated without stopping the transmission using thepilot channel.

An embodiment of the present invention will be described next withreference to FIGS. 4 to 6.

FIG. 4 is a block diagram showing an example of the arrangement of atransmission section corresponding to data channel N.

FIG. 5 is a block diagram showing an example of the arrangement of atransmission/reception section corresponding to data channel M.

FIG. 6 is a block diagram showing an example of the arrangement of aweighting matrix for antenna and antenna elements.

Referring to FIG. 4, a transmission section for a pilot channel in thisembodiment includes a spreading circuit 401 for spreading dataconsisting of “0”s alone by multiplying the data by a spread codeSC_(N)(Tx), a spread code generating circuit 403 for generating thespread code SC_(N)(Tx), and a transmission power control circuit 402 forcontrolling the transmission power for the spread signal. Differentspread codes are assigned to the respective channels and hence used asmeans for discriminating the channels in code division multiple access(CDMA) sharing the same frequency among all the channels.

Referring to FIG. 5, a data channel trans-mission/reception means inthis embodiment includes a spreading circuit 501 for spreadingtransmission data d_(M)(Tx) with a transmission spread code SC_(M)(Tx),a transmission power control circuit 502 for controlling thetransmission power for the spread signal, a spread code generatingcircuit 503 for generating the transmission spread code SC_(M)(Tx) and areception spread code SC_(M)(Rx), a delay circuit 504 for delaying thereception spread code SC_(M)(Rx) in accordance with a delay in each pathof multipath channels for reception signals, de-spreading circuits 505that are equal in number to the paths and multiply the delayed receptionspread signals and the reception signals through the data channels,integration circuits 506 that are equal in number to the paths andcumulatively add the de-spread signals for a 1-symbol time, and a RAKEcombining demodulation circuit 507 for combining the outputs from theintegration circuits 506 corresponding to the respective paths in phaseat a maximum ratio.

Referring to FIG. 6, a weighting matrix for antenna on the transmissionside in this embodiment includes weighting circuits 601 and 602 forweighting signals (including amplitudes and phases) to be output to therespective antenna elements over transmission signals on the respectivechannels with weighting coefficients {W} supplied from the controlsection, addition circuits 605 that are equal in number to the antennaelements, each circuit adding/combining transmission signals in eachchannel, duplexers 606 which are equal in number to the antenna element,each allowing one antenna element to be used for transmission andreception, and a plurality of antenna elements 607. Similarly, on thereception side, the matrix includes a weighting circuit 603 forweighting the signal (including the amplitude and phase) received byeach antenna element with a weighting coefficient {W} supplied from thecontrol section, and an addition circuit 604 for adding/combining therespective weighted reception signals.

The operation of the cellular system according to the present inventionwill be described next with reference to FIG. 6.

As in the basic aspect of the present invention described above, whendata communication is to be started, the directivity of each receptionantenna is determined to maximize the signal-to-interference ratio (SIR)of a received signal. More specifically, it suffices if weightingcoefficients {W_(M) 1′, W_(M) 2′, . . . } are determined to maximize theshort-time average of SIRs. In addition, the transmission directivity ofeach data channel is determined to have the same antenna directivity asthat used for reception. In an ideal radio system (the gain and phasecharacteristics remain unchanged in transmission and reception), itsuffices if coefficients complex conjugate to the weighting coefficients{W_(M) 1′, W_(M) 2′, . . . } used for reception are used as transmissionweighting coefficients {W_(M) 1′, W_(M) 2′, . . . }.

The above operation may be simplified by limiting the weightingcoefficients {W_(M) 1′, W_(M) 2′, . . . } and {W_(M) 1′, W_(M) 2′, . . .} to “1”s and “1”s alone. That is, one (or a plurality) of antennas towhich directivities are assigned in advance is selected and used fortransmission/reception. In this case, the directivity in transmissioncan be easily matched with that in reception. This can greatly reducethe processing amount for antenna directivity determination and simplifyadjustments to the gain and phase of the radio system. However, thedegree of freedom in antenna directivity is limited.

Data channels can be made to correspond to pilot channels by notifyingthe spread codes used in the respective channels. The transmission powerfor a pilot channel or data channel is controlled to 0 (OFF) to preventunnecessary interference from disturbing other channels in use.

1. A base station in a cellular system, the cellular system including atleast one mobile terminal, said base station comprising: a transmitterwhich transmits first and second pilot channels and transmits first andsecond data channels, the second data channel being a high bit ratechannel which has a higher bit rate than that of the first data channel,the first and the second pilot channels being made to correspond to thefirst and the second data channels, respectively; and a controller whichnotifies the mobile terminal that the second pilot channel is made tocorrespond to the second data channel, the mobile terminal being allowedto communicate by making use of the second data channel.
 2. The basestation according to claim 1, wherein said transmitter transmits a thirddata channel, and the first pilot channel is made to correspond to thethird data channel and is shared by the first and the third datachannels.
 3. The base station according to claim 2, wherein the secondpilot channel is exclusively assigned to the second data channel.
 4. Thebase station according to claim 1, wherein the second pilot channel hasa narrow directivity which is narrower than that of the first pilotchannel.
 5. The base station according to claim 1, further comprising anantenna which has plural types of directivities, wherein a directivityof each of the first and the second pilot channels is set by choosingone type of directivity from the plural types of directivities.
 6. Thebase station according to claim 1, wherein said transmitter transmits acontrol channel toward plural mobile terminals, and said controllernotifies, via the control channel, a specific mobile terminal of theplural mobile terminals that the second pilot channel is made tocorrespond to the second data channel.
 7. A base station in a cellularsystem, the cellular system including at least one mobile terminal, saidbase station comprising: a transmitter which transmits plural pilotchannels and transmits a data channel to said mobile terminal, the datachannel being made to correspond to a specific pilot channel among saidplural pilot channels in the event that the mobile terminal moves at ahigh speed; and a controller which notifies the mobile terminal that thedata channel is made to correspond to the specific pilot channel in theevent that the mobile terminal moves at a high speed.
 8. The basestation according to claim 7, wherein the specific pilot channel has awider directivity than that of each of other pilot channels.
 9. The basestation according to claim 7, wherein the specific pilot channel has adirectivity which covers all directions.
 10. A base station in acellular system, the cellular system including at least one mobileterminal, said base station comprising: a transmitter which transmitsplural pilot channels and transmits a data channel to the mobileterminal, the data channel being made to correspond to a specific pilotchannel among the plural pilot channels in the event that a position ofthe mobile terminal is unknown by the cellular system; and a controllerwhich notifies the mobile terminal that the data channel being made tocorrespond to the specific pilot channel in the event that a position ofthe mobile terminal is unknown by the cellular system.
 11. A basestation in a cellular system, the cellular system including pluralmobile terminals, said base station comprising: a transmitter whichtransmits plural pilot channels and transmits plural data channels tothe plural mobile terminals, the plural pilot channels and the pluraldata channels being transmitted via an antenna, which has plural typesof directivities, one of the plural types of directivities being usedfor each of the plural data channels, and the correspondence between theplural pilot channels and the plural data channels being determined onthe basis of a directivity used for each of the plural data channels;and a controller which notifies the plural mobile terminals of thecorrespondence between the plural pilot channels and the plural datachannels.
 12. The base station according to claim 11, wherein thedirectivity used for each of the plural data channels is set inaccordance with a position of each of the plural mobile terminals whichreceive the plural data channels, respectively.
 13. A base station in acellular system, the cellular system including at least one mobileterminal, said base station comprising: a transmitting means fortransmitting first and second pilot channels and transmitting first andsecond data channels, the second data channel being a high rate channelwhich has a higher bit rate than that of the first data channel, thefirst and the second pilot channels being made to correspond to thefirst and the second data channels, respectively; and a controllingmeans for notifying the mobile terminal that the second pilot channel ismade to correspond to the second data channel, the mobile terminal beingallowed to communicate by making use of the second data channel.
 14. Abase station in a cellular system, the cellular system including atleast one mobile terminal, said base station comprising: a transmittingmeans for transmitting plural pilot channels and transmitting a datachannel to the mobile terminal, the data channel being made tocorrespond to a specific pilot channel among the plural pilot channelsin the event that the mobile terminal moves at a high speed; and acontrolling means for notifying the mobile terminal that the datachannel being made to correspond to the specific pilot channel in theevent that the mobile terminal moves at a high speed.
 15. A base stationin a cellular system, the cellular system including at least one mobileterminal, said base station comprising: a transmitting means fortransmitting plural pilot channels and transmitting a data channel tothe mobile terminal, the data channel being made to correspond to aspecific pilot channel among the plural pilot channels in the event thata position of the mobile terminal is unknown by the cellular system; anda controlling means for notifying the mobile terminal that the datachannel being made to correspond to the specific pilot channel in theevent that a position of the mobile terminal is unknown by the cellularsystem.
 16. A base station in a cellular system, the cellular systemincluding plural mobile terminals, said base station comprising: atransmitter means for transmitting plural pilot channels andtransmitting plural data channels to the plural mobile terminals, theplural pilot channels and the plural data channels being transmitted viaan antenna, which has plural types of directivities, one of the pluraltypes of directivities being used for each of the plural data channels,and the correspondence between the plural pilot channels and the pluraldata channels being determined on the basis of a directivity used foreach of the plural data channels; and a controlling means for notifyingthe plural mobile terminals of the correspondence between the pluralpilot channels and the plural data channels.
 17. A cellular system,comprising: a base station; and at least one mobile terminal, whereinsaid base station transmits first and second pilot channels andtransmits first and second data channels, the second data channel beinga high rate channel which has a higher bit rate than that of the firstdata channel, the first and the second pilot channels being made tocorrespond to the first and the second data channels, respectively, andsaid base station notifies the mobile terminal that the second pilotchannel is made to correspond to the second data channel, and whereinsaid mobile terminal is allowed to communicate by making use of thesecond data channel and receives the notification from said basestation.
 18. A cellular system, comprising: a base station; and pluralmobile terminals, wherein said base station transmits plural pilotchannels and transmits plural data channels to the plural mobileterminals, the plural pilot channels and the plural data channels beingtransmitted via an antenna, which has plural types of directivities, oneof the plural types of directivities being used for each of the pluraldata channels, and the correspondence between the plural pilot channelsand the plural data channels being determined on the basis of adirectivity used for each of the plural data channels, and said basestation notifies the mobile terminal that the second pilot channel ismade to correspond to the second data channel, and wherein said mobileterminal is allowed to communicate by making use of one of the pluraldata channels and receives the notification from said base station. 19.A controlling method for use in a cellular system, the cellular systemincluding a mobile terminal, said controlling method comprising:transmitting first and second pilot channels; transmitting first andsecond data channels, the second data channel being a high rate channelwhich has a higher hit rate than that of the first data channel, thefirst and the second pilot channels being made to correspond to thefirst and the second data channels, respectively; and notifying themobile terminal that the second pilot channel is made to correspond tothe second data channel, the mobile terminal is allowed to communicateby making use of the second data channel.
 20. A controlling method foruse in a cellular system, the cellular system including plural mobileterminals, said controlling method comprising: transmitting plural pilotchannels; transmitting plural data channels to said plural mobileterminals, the plural pilot channels and the plural data channels beingtransmitted via an antenna, which has plural types of directivities;using one of the plural types of directivities used for each of theplural data channels; determining the correspondence between the pluralpilot channels and the plural data channels on the basis of adirectivity used for each of the plural data channels, and notifying theplural mobile terminals of the correspondence between the plural pilotand the plural data channels.